The present invention relates to a sample examination method using a scanning electron microscope (“SEM,” hereafter) that irradiates an electron beam on a pattern formed on a semiconductor wafer in-line in semiconductor front-end processes during the manufacture and that detects electron occurring from an irradiated position. More specifically, the invention relates to a defect display method used with the review SEM for view of in greater detail a defect detected on a semiconductor wafer.
In a current semiconductor production process, defect review is carried out for cause investigation of a defect occurred on a semiconductor wafer in-line of the manufacture. Conventionally, optical microscopes have been used for, for example, defect detection and view purposes. However, in recent years, with semiconductor patterns being smaller, countermeasures have become necessary to address defects of several tens of nanometers in size, such that SEM methods for defect detection and reviewing have been prevailing.
According to an review SEM, such as described above, for review of a defect of the semiconductor, a targeted substrate (sample) is moved toward defect coordinates output from a defect detector, and then the defect is imaged at a high magnification factor (“high magnification,” hereinafter). However, the accuracy of the defect coordinates output by the defect detector is low with respect to the field of view of a high magnification image. As such, first, a defective image is acquired imaged at a low magnification factor (“low magnification,” hereinafter), and then is acquired at high magnification.
In addition, depending on the case, in, for example, defect review for bare wafers, the accuracy of the defect coordinates output by the defect detector is low with respect to the field of view of a low magnification image. In this case, for example, the accuracy of a defect position is improved by imaging the defect by using an optical microscope appended to the review SEM. Then, the defect position is identified by imaging the defect at a low magnification factor, and then finally, the defect is imaged at a high magnification factor at the defect position.
In acquiring images at the low and high magnification factors by using the review SEM, a plurality of detectors are used. Thereby, a plurality of images indicative of different features of a sample are created. In addition, depending on the system, the configuration includes an EDX (energy dispersion X-ray spectrum) function. The EDX function irradiates an electron beam onto a sample, detects an X-ray emitted from a neighboring portion of a defective portion, and thereby calculates an energy distribution of the X-ray, whereby to examine the composition of the defect.
It is necessary to take countermeasures by analyzing the cause of defect occurrence after defect imaging. Normally, the review SEM includes an automatic defect classifying function as a support function for cause analysis for defects. The automatic defect classifying function acquires feature values of an SEM image, such as defect sizes, shapes, and textures, as detail information from a high magnification defect image. Then, the function classifies the types of defects in accordance with the detail information.
In many cases, other support functions for analyzing the causes of defect occurrences include a defect image display function that displays acquired defect images or outputs (prints) onto a paper sheet. The defect image display function includes, for example, a thumbnail display screen and a detail display screen. The thumbnail display screen displays, for example, thumbnail images, thereby to display many defects on one screen. The detail display screen displays, for example, many images and signals of respective defects. Such the defect image display function is also capable of display defects corresponding to respective defect types classified by, for example, the automatic defect classifying function.
As a method of acquiring an image taken of a sample as diagonally viewed through an SEM, Japanese Unexamined Patent Application Publication No. 2001-15055 discloses a method for acquiring an image by setting the incidence direction of electron beam being irradiating onto a sample to a diagonal direction with respect to the surface of the sample.